This invention relates to polyblends and more specifically to polyblends of polyphenylene oxide (PPO)with styrene(S)/acrylonitrile (AN) copolymers which may optionally be modified with rubber.
U.S. Pat. No. 3,383,435 discloses blends of polyphenylene oxide and one or more of homopolystyrene (PS), styrene/acrylonitrile/butadiene polymers (ABS), and rubber-modified polystyrene (HIPS). Commercial interest, however, has focused on PPO blends containing HIPS since these have physical properties making them particularly suitable as molding resins. It is generally known, that the presence of AN in an ABS or SAN copolymer provides solvent resistance to parts molded therefrom and such a property is desirable in PPO blends intended for such applications.
U.S. Pat. No. 4,360,618 discloses blends of PPO and AN-containing polymers in which the levels of AN in the latter are between 2 and 8% by weight. Polyblends with higher AN content were found therein to have poor mechanical properties which suggests that as the AN content of the AN-containing polymer is increased, the compatibility of the two polymers is decreased, resulting in loss of heat distortion resistance and impact strength.
U.S. Pat. No. 4,405,753 discloses blends of PPO and AN-containing polymers in which the AN content of the latter can be increased up to 15% by weight, but a third copolymer of styrene/maleic anhydride is required in the blend to retain good mechanical properties when the AN content is above about 8%.